Re: [PATCH 0/5] rtcache remove respin

From: Eric Dumazet <redacted>
Date: Mon, 02 Jul 2012 12:44:01 +0200

On Sun, 2012-07-01 at 05:02 -0700, David Miller wrote:

quoted

It's been a while and there were of course a lot of merge hassles with
the most recent set I posted, so I respun these patches tonight
because I wanted to see the effects of the recent rpfilter hacks on an
rtcache-less system.

On a SPARC T3-1:

1) Output route lookup: ~2800 cycles
2) Input route lookups: ~3000 cycles (rpfilter=0)
                        ~4300 cycles (rpfilter=1)

Another nice part is how small struct rtable is after this patch set:

struct rtable {
	struct dst_entry        dst;
	int                     rt_genid;
	unsigned int            rt_flags;
	__u16                   rt_type;
	__be32                  rt_dst;
	int                     rt_route_iif;
	int                     rt_iif;
	int                     rt_oif;
	__be32                  rt_gateway;
	u32                     rt_peer_genid;
	unsigned long           _peer;
	struct fib_info         *fi;
};

which is about 208 bytes on sparc64.

Signed-off-by: David S. Miller <davem@davemloft.net>

Can be <= 192 actually

rcu_head not needed anymore in dst_entry

If we still want __refcnt being on cache line boundary, we might find a
better way to accomplish this.

Once we can actually check something like this in, rt_dst is
guarenteed to be eliminated as well.

The dst neighbour pointer will also be gone.

So lots of shrinking still to go and yes we'll need to reposition
that __refcnt member carefully.